This invention relates to a bobbin lead roving machine and more particularly to a method for controlling the take-up or winding tension placed on the roving through adjustment of the r.p.m. of the bobbin, and an apparatus for carrying out such method.
In a roving machine, the rate of increase in the bobbin diameter relative to the increase in the number of roving layers on the bobbin is changed with spinning conditions such as the kind and weight of the fibers to be roved, the r.p.m. of the flyer, or the number of twists. Thus, when a single set of cone drums are used, it is difficult to adjust the roving machine so that the roving take-up tension may be constant from the beginning until the end of winding on a bobbin under any spinning conditions. Since fluctuations in the roving tension may cause fluctuations in the weight of the roving and in the number of roving, higher skill and experience on the part of the operators are required for adjusting the tension placed on the roving to an optimum value.
So far, various methods and devices have been proposed to effect the roving operation under a constant roving tension. Thus the devices shown in the Japanese Patent Publication No. 48652/1977 and the Japanese Utility Model Publication No. 13376/1977 are being used practically in a roving machine making use of cone drums as means for changing the speed of rotation of the bobbin. In known devices, a tentative roving operation is performed under given spinning conditions. During such tentative spinning, the state of tension on the roving travelling between the front roller and the flyer top is checked several times from the beginning until the end of winding for adjusting the cone drum belt shift compensation device and changing the cone drum belt position by means of a belt shifter. When the desired r.p.m. of the bobbin is reached, the position of the belt shifter of the compensation device is set for fixing the relation between the number of the roving layers and the corresponding cone drum belt position or displacement. The actual spinning operation is contemplated to be performed under a constant roving tension by observing the above relation during spinning.
In this known method, the relation between the number of the roving layers and the cone belt position is fixed on the assumption that the relation between the cone drum belt position and the r.p.m. of the bobbin can be fixed unequivocally by thus fixing the relation between the number of the roving layers and the belt position. However, the same r.p.m. of the bobbin may not be necessarily obtained for the same belt positions because of other factors such as changes in the load status, decrease in the power of transmission due to prolonged use of the transmission belt, and changes in belt tension.
It is therefore a principal object of the present invention to provide a method and apparatus for controlling the take-up tension on the roving whereby the tension on the roving may be kept constant under any spinning conditions or states of the roving machine.